Apparatus and method for generating heat



Max-ch28, 1967 J. w. WINZELER ETAL 3,311,735

APPARATUS AND METHOD FOR GENERATING HEAT 2 Sheets-Sheet 1 Original FiledMay 22,. 1961 CURRENT CURRENT m B 8 R M. and l. Rs Y Z EER E I. 2 K O NN CT R mwm o w G a V n la n 2 W A F l H mm 6 w F GAS SOURCE CURRENTSOURCE March 28, 1967 J,W.W]NZELER ETAL 3,311,735

APPARATUS AND METHOD FOR GENERATING HEAT Original Filed May 22, 1961 2Sheets$heet 2 G S UR A 50 CE 35 CURRENT SOURCE CURRENT SOURCE 38 FIG.lo.

JOHN W. WINZELER JAMES F. TUCKER INVENTORS.

ATTORNEY.

United States Patent M 3,311,735 APPARATUS AND METHOD FOR GENERATINGHEAT John W. Winzeier and James F. Tucker, Santa Ana, Califl, assignorsto Giannini Scientific Corporation, Santa Ana, Califi, a corporation ofDelaware Continuation of application Ser. No. 111,763, May 22, 1961.This application May 21, 1964, Ser. No. 369,188 6 Claims. (Cl. 219-121)This invention relates to an apparatus and method for heating aworkpiece for cutting, welding, and other purposes. This application isa continuation of patent application Serial No. 111,763, filed May 22,1961, for Apparatus and Method for Generating Heat, now abandoned.

An object of the invention is to provide an apparatus and method forintroducing a great amount of heat into a workpiece in a highlyefiicient manner which is susceptible of accurate control.

Another object is to provide a method and apparatus for cutting andwelding metallic workpieces by passing a large electric current througha stream of plasma from a plasma torch, such current being independentof the current passed through the arc of such torch.

Another object is to provide a method and apparatus for effectingmachining of a workpiece by regulating the voltage impressed betweensuch workpiece and an electrical plasma-jet torch of the transferred-arctype.

A further object is to provide a method and apparatus for effectinghighly accurate electric-arc machining, and effecting punching of holes.

Another object is to provide an electric arc apparatus in the nature ofa band saw.

Another object is to provide a workpiece-heating method and apparatusemploying at least two independent electrical circuits and utilizingeither AC. or D.C., or both AC. and DC.

These and other objects and advantages of the invention will be morefully set forth in the following specification and claims, considered inconnection with the attached drawings to which they relate.

In the drawings:

FIGURE 1 is a schematic longitudinal central sectional View illustratingan apparatus, constructed in accordance with the present invention, asemployed in cutting a metallic workpiece;

FIGURE la corresponds to FIGURE 1 but illustrates the welding of a pairof workpieces;

FIGURE 2 is a transverse section taken on line 22 of FIGURE 1 andillustrating the tangential introduction of gas into the apparatus; and

FIGURE 3 is a schematic view, partially in side elevation and partiallyin section, illustrating an arc apparatus which operates in the mannerof a band saw.

Referring first to the embodiment of FIGURES l and 2, an electricalplasma-jet torch is indicated generally at and has a non-consumablemetal nozzle electrode 11 formed with an elongated cylindrical passageor opening 12. The upper end of passage 12 communicates with acylindrical gas vortex chamber 13 having a frustoconical central portionor extension. The frustoconical wall 14 of such central portion orextension merges, at its narrow end, with the wall of passage 12.

The non-consumable metal back electrode 16 of the illustrated torch isconical in shape, the cone angle corresponding generally to that of wall14. The tip of the back electrode is disposed in the frustoconicalextension of vortex chamber 13, being spaced from wall 14 to form afrustoconical channel therebetween. The main body of the back electrodeis disposed in the main or relatively large portion of vortex chamber13, and has a radial 3,3ll,735 Patented Mar. .28, 1967 flange 17 theperipheral wall of which is cylindrical in shape.

Flange 17 seats sealingly against the bottom of an inverted metal cup18. The side wall of cup 13 is telescoped into a generally tubular endportion 19 of nozzle electrode 11, there being an insulating sleeve 21provided between the cup wall and the tubular portion 19 in order tomaintain the nozzle and back electrodes insulated from each other.

The internal surface of the cup side wall, and the exposed interiorsurface of insulating sleeve 21, are flush with each other and form thecylindrical wall of vortex chamber 13. Such cylindrical wall has adiameter substantially greater than the cylindrical wall of flange 17,in order to permit introduction of gas therebetween as will next bedescribed.

Gas is introduced into chamber 13 from a suitable gas source which isrepresented schematically at 22. The gas conduit 23 from source 22communicates tangentially (FIGURE 2) with chamber 13 at a point locatedradially-outwardly from flange 17. A suitable gas, such as nitrogen, isthus introduced tangentially so that it will flow vortically around theback electrode 16. The gas then flows vortically and helically throughthe channel around the tip of the back electrode, and then flowsvortically and helically through nozzle passage 12.

The nozzle electrode 11 is formed with an annular cooling chamber 24around the nozzle passage and also around wall 14. Water is passedthrough such chamber, and through a cooling chamber 26 in back electrode16, by means of various conduits which are indicated at 27.

Mounted coaxially of nozzle electrode 11, in spaced relationship fromthe lower end thereof, is an additional non-consumable electrode 28 ofannular shape. Such electrode, which may be formed of copper, tungstenor the like, has an opening 29 the diameter of which correspondsgenerally to that of the nozzle passage 12 with which it is registered.The additional electrode 28 is insulated from nozzle electrode 11 bymeans of a disc 31 formed of a suitable heat-resistant ceramic, suchdisc having an opening registered with and corresponding to the opening29, or else having an opening substantially larger than opening 29. Theadditional electrode is formed with an annular coolant chamber 32through which water is passed by means of conduits 33.

A first current source 35 is connected through leads 36 and 37,respectively, to the cup 18 and to nozzle electrode 11. Since thecurrent in cup 18 flows through the adjacent back electrode to the tipthereof, an electric arc may thus be maintained in passage 12 betweenthe tip of back electrode 16 and the wall of the passage 12. The currentsource 35 may be a source of either DC. or AC, preferably D.C. so thatcontinuous ionization takes place, and should be adapted to deliverrelatively large currents although not necessarily as large as thosedelivered by a second current source which is indicated at 38.

The second source 38 is connected, through leads 39 and 40,respectively, between the additional electrode 28 and the work 41, suchwork being indicated in FIG- URE 1 is a metal plate to be cut. Thesecond source 38 is adapted to deliver extremely large currents and maycomprise a DC. source or an AC. source, either single or multi-phase.Furthermore, the second source may comprise a circuit (such ascontaining a capacitor or bank thereof) adapted to deliver a large pulseof current at predetermined time intervals.

Description of various methods, particularly relative to the embodimetof FIGURES 1-2 A stream of hot ionized gas is generated by theelectrical plasma-jet torch 19, namely by introducing gas tangentiallyfrom source 22 into the gas vortex chamber 13 and thence through thefrustoconical chamber adjacent wall 14 to the passage or opening 12 inthe nozzle electrode. The combination of such gas flow and the electricare, which is maintained in passage 12 due to application of voltagefrom source 35, generates a high-velocity stream of ionized plasma asindicated at 42. Such plasma is directed against the metallic workpiece41, as illustrated in FIGURE 1, and the second current source 38 isapplied to maintain a second and separate electric are through theplasma 42 between the workpiece and the additional electrode 28.

In the showing of FIGURE 1, the method is employed to effect cutting ofthe workpiece 41, the kerf being indicated at 43. Cutting isaccomplished by making the voltage of source 38 sufficiently high thatthe arc and plasma reach clear to the lower surface of the workpiece 41to cut the same, the dross being ejected downwardly as indicated.

In order to reduce the cost of electricity, and as previously indicated,the current source 38 may be a source of A.C. power, such as threephase. Many hundreds of amperes of current may thus be caused to flowthrough the external plasma stream 42 to the workpiece 41 without in anyway affecting the electrodes 11 and 16 of torch 10.

It is a feature of the invention that the apparatus may be employed toeffect machining of a workpiece, for example a metal workpiece beingrotated in a lathe. This is accomplished by progressively varying thevoltage impressed by source 38 between electrode 28 and the workpiece41. Such variation in voltage changes the length of the plasma jet-arc42 to regulate the depth of cut in the workpiece. Thus, when theworkpiece in a lathe is to be cut to a relatively small diameter, thevoltage is increased. Conversely, the voltage is reduced when thediameter is to be relatively large. Machining is thus effected in ahighly simple and effective manner and without the necessity of movingthe apparatus -28 toward or away from the work.

To heat the workpiece 41 or to weld the same, as distinguished fromcutting the workpiece, the amount of electrical power introduced fromsource 38 is normally reduced. The work, comprising two abutted metalplates, may be either negative or positive.

It is to be understood that when the method and apparatus are employedin welding a workpiece, filler metal may be introduced into the moltenweld puddle (in the form of wire, powder, etc.) from any conventionalsource. Also, various fluxes, shields of inert gas, etc., may beemployed in conventional manner. Referring to FIGURE 1a, the workpiecesto be welded are numbered 41a and 4112, the filler wire being indicatedat 41c. Except as indicated, the numbers in FIGURE 1a correspond toFIGURE 1.

As previously stated, it is a feature of the invention that the currentsource 38 may be a pulse means, such as a bank of capacitors andassociated triggering and charging apparatus. In such a system, thecurrent generated by the discharging capacitors passes down the streamof plasma 42, so that the location of the point of impingemeat againstthe workpiece 41. is accurately determined and controlled. Cutting,heating and welding may thus be controlled in a highly accurate manner.For example, the discharge of a very large capacitor means is operativeto punch a hole in the workpiece 41, the location of the hole beingaccurately determined. Furthermore, repetitive discharging of capacitormeans may effect accurate spark or arc-machining of square holes, andother irregular shapes, or irregular gouges or grooves.

Embodiment of FIGURE 3 The apparatus of FIGURE 3 is identical to that ofFIGURES 1 and 2 except that the metallic workpiece 41 is replaced by ametal disc 46 (formed of copper, tungsten,

etc.) which is rotated at a substantial rate of speed by an electricmotor 47. The current source 38 is connected between electrode 28 andthe disc 46, the current connection to the disc being through a slipring 48 on the electrically-conductive shaft 49 which associates themotor 47 with the center of the disc.

Disc 46 is formed with a coolant chamber 51 through which water ispassed by means of a suitable inlet fitting 52 adapted to introducewater into the shaft 49 regardless of the rotated position of thelatter. From fitting 52, the water flows into chamber 51 and thendischarges (into an unshown collector) through an opening 53 at theperiphery of the disc. Alternatively, the discharge may be through theshaft 49.

The apparatus further comprises a horizontal support plate 55 having anopening 56 therein through which the plasma and are 42 may pass. It isto be understood that the plate 55 is suitably supported in fixedrelationship, although it may be adjustable to various heights. Theopening 56 is sufficiently large that the material forming the plate 55will not be melted.

In performing the method with the apparatus of FIG- URE 3, motor 47 isemployed to rotate the disc 46, and water is passed therethrough. Theapparatus described relative to FIGURES 1 and 2 is so disposed that thejet and are 42 pass through the opening 56 to a peripheral portion ofthe upper surface of the disc 46. The speed of rotation of disc 46, andthe amount of water cooling, are so correlated to the power suppliedfrom current source 38 that the disc 46 is not melted. An object to becut is then disposed on the support 55 and is moved across the jet 42 inthe manner of the movement of a workpiece in a band saw or jig saw.

In the described manner, both conductors and nonconductors may bereadily cut without the necessity of making electrical connectionthereto. Suitable means may be provided to remove the dross and preventundesired buildup thereof on the electrode 46.

It is to be understood that, in the embodiments of FIGURES 1-3, anadditional A.C. or D.C. current source may be connected betweenelectrode 28 and nozzle electrode 11, thereby adding further energy tothe plasma which forms the jet 42. It is also to be understood, relativeto the embodiments of FIGURES 1-3, that source 38 may be a source ofhigh-frequency current-such as in the radio frequency range. R.F.current may also be superimposed on a D.C. or low-frequency A.C. source38. Such use of high frequencies produces an effect in the nature of amechanical vibration, and aids in breaking down the scale which ispresent on the surface of the work.

Specific examples The following is a specific example of the situationin which the embodiment of FIGURES 1 and 2 is employed for cutting. Theworkpiece, which may comprise a mild steel plate three inches thick, isdisposed about one-quarter inch from electrode 28. First current source35 is caused to supply 1,000 amperes DC. at 36 volts, the nozzleelectrode being positive with respect to the back electrode. Secondcurrent source 38 is caused to supply 1,000 amperes at 40 volts, eitherA.C. or D.C. (work positive). The gas source 22 may be caused to supplyargon at a rate of about 30 cubic feet per hour.

The following is a specific example of the situation in which theembodiment of FIGURES 1 and 2 is employed for welding. Two mild steelplates, each one-half inch thick, are butted against each other and sodisposed that the abutted edges are about one-quarter inch fromelectrode 23. First current source 35 is caused to supply 250 amperesD.C. at 25 volts, the nozzle electrode being positive with respect tothe back electrode. Second current source 38 is caused to supply 125amperes at 60 volts, either A.C. or D.C. (work positive). The gas source22 is caused to supply argon at a rate of about 30 cubic feet per hour.Filler metal may be supplied in power or stick (wire) form. A blanket ofgranular flux may be disposed along the seam, or gas-shieldingtechniques may be employed.

The apparatus employed relative to both specific examples may have anozzle diameter of about one-quarter inch. A high-frequency source, forexample producing 100 kilocycles, may be employed as previouslyindicated.

Various embodiments of the present invention, in addition to what hasbeen illustrated and described in detail, may be employed withoutdeparting from the scope of the accompanying claims.

We claim:

1. Apparatus for heating a metal workpiece, which comprises anelectrical plasma-jet torch having a back electrode and a nozzleelectrode, means to pass gas between said back and nozzle electrodes andthrough the nozzle opening in said nozzle electrode to the vicinity ofsaid workpiece, means to maintain an electric are between said back andnozzle electrodes to thereby efiect heating and ionization of said gas,a non-consumable additional electrode disposed between said nozzleelectrode and said workpiece in spaced relationship from said workpiece,said additional electrode being insulated from said nozzle electrode andhaving an opening therein through which said ionized gas passes intraveling from said nozzle electrode to the vicinity of said workpiece,and means independent of said back electrode to maintain a second arebetween said adidtional electrode and said workpiece through saidionized gas, said last-named means comprising means to efifect betweensaid additional electrode and said workpiece a pulse discharge of shortduration.

2. Electrical apparatus in the nature of a band saw, comprising anelectrical plasma-jet torch adapted to discharge a stream of hot ionizedgas, an additional electrode spaced from said torch and in suchrelationship thereto that the ionized gas emanating from said torchreaches the vicinity of said additional electrode, means to maintain ahigh-current electric are between said torch and said additionalelectrode through said ionized gas, and means to revent rapiddeterioration of said additional electrode.

3. The invention as claimed in claim 2, in which means are providedbetween said torch and said additional elec trode to support aworkpiece, said means being adapted to permit passage of said ionizedgas and said are to said additional electrode.

4. The invention as claimed in claim 2, in which said are means includesa current source connected between a front electrode of said torch andsaid additional electrode.

5. A method of effecting accurate metal-removal operations relative to aworkpiece, which comprises directing a stream of ionized gas from anelectrical plasma-jet torch to the vicinity of an electricallyconductive workpiece at a precisely located portion of said workpiece,and discharging a large pulse of current through said gas to saidportion of said workpiece to effect removal of a quantity of metal fromsaid portion of said workpiece.

6. A method of melting a portion of an electricallyconductive workpiece,which comprises employing an electrical plasma-jet torch to direct astream of plasma to the vicinity of an electrically-conductiveworkpiece, and effecting flow of a high-frequency current through saidstream of plasma and in a circuit including said workpiece, saidhigh-frequency current aiding in the removal of scale from saidworkpiece.

References Cited by the Examiner UNITED STATES PATENTS 2,806,124 9/1957Gage 219--121 2,858,411 10/1958 Gage 21975 2,874,265 2/1959 Reed et al.219-121 2,929,952 3/1960 Giannini 31323l 2,945,119 7/1960 Blackman2l9123 2,972,698 2/1961 Dana et a1 313-231 3,149,222 9/1964 Giannini etal. 3l3231 X JOSEPH V. TRUHE, Primary Examiner.

1. APPARATUS FOR HEATING A METAL WORKPIECE, WHICH COMPRISES ANELECTRICAL PLASMA-JET TORCH HAVING A BACK ELECTRODE AND A NOZZLEELECTRODE, MEANS TO PASS GAS BETWEEN SAID BACK AND NOZZLE ELECTRODES ANDTHROUGH THE NOZZLE OPENING IN SAID NOZZLE ELECTRODE TO THE VICINITY OFSAID WORKPIECE, MEANS TO MAINTAIN AN ELECTRIC ARC BETWEEN SAID BACK ANDNOZZLE ELECTRODES TO THEREBY EFFECT HEATING AND IONIZATION OF SAID GAS,A NON-CONSUMABLE ADDITIONAL ELECTRODE DISPOSED BETWEEN SAID NOZZLEELECTRODE AND SAID WORKPIECE IN SPACED RELATIONSHIP FROM SAID WORKPIECE,SAID ADDITIONAL ELECTRODE BEING INSULATED FROM SAID NOZZLE ELECTRODE ANDHAVING AN OPENING THEREIN THROUGH WHICH SAID IONIZED GAS PASSES INTRAVELING FROM SAID NOZZLE ELECTRODE TO THE VICINITY OF SAID WORKPIECE,AND MEANS INDEPENDENT OF SAID BACK ELECTRODE TO MAINTAIN A SECOND ARCBETWEEN SAID ADDITIONAL ELECTRODE AND SAID WORKPIECE THROUGH SAIDIONIZED GAS, SAID LAST-NAMED MEANS COMPRISING MEANS TO EFFECT BETWEENSAID ADDITIONAL ELECTRODE AND SAID WORKPIECE A PULSE DISCHARGE OF SHORTDURATION.